CN1713869A - Artificial intervertebral disc - Google Patents

Abstract

Artificial intervertebral disc, comprising a nucleus of flexible material wi th the shape of a flattened body, with a lower and an upper side connected by a lateral surface, having a rounded-preferably circular or ellipsoid-shape, around which at least substantially radially oriented windings of a traction - resistant fibre have been applied. The fibres have a tensile strength of at least 1 GPa and a modulus of at least 10 GPa.

Description

Artificial intervertebral disc

The present invention relates to artificial intervertebral disc.

From US 6,375, known such dish in 682.This known dish is made up of the intermediate system of localized toward each other two metallic plates and corrugated tube (bellows) and spring, each metallic plate is pasting the relative side of the successive vertebral body of two joints, and each metallic plate is connected on it, and described intermediate system allows the motion between metallic plate and the coupled vertebral body.

This known structure has following defective: it mechanically is complicated, and owing to use hard material, for example with the contacted metal of body part, this may cause adaptability problem.

Now, the purpose of this invention is to provide a kind of artificial intervertebral disc, it can prevent the defective of known dish to a great extent.

According to the present invention, this purpose reaches, because described dish contains the nuclear that flexible material is made, has applied the traction-resistant fibre twister around this nuclear.

Dish according to the present invention has simple structure, only contains softer material relatively, and because the flexibility of this nuclear, described dish can adapt to the vertebral body of placing this dish betwixt well.Further advantage is: can extend to the major part of vertebral body according to dish of the present invention, or even whole surface, therefore, result from epispinal power and be actually and born by whole vertebral body.Consider needed mobility each other, known dish is little more a lot of than the vertebral body of placing this dish betwixt usually, therefore may produce high localised load therein.Can follow vertebral body equally big according to dish of the present invention, and still allow the mutual mobility of the height of vertebral body.

Dish according to the present invention comprises the softish nuclear with flat partially shape, has the upper side and the downside that link to each other by side surface." softish " is understood that at this described material has low shear modulus.This modulus is preferably 50MPa at the most, more preferably 20MPa at the most.In fact, this modulus can be subjected to anyly restrictedly to reduce hardly, but makes extra measure to be taked less than the modulus of shearing of 1MPa, with described nuclear in fact liquid thickly encapsulate.The elongation at break of described nuclear is preferably and is higher than 20%, more preferably is higher than 100%.The upper limit of this character is actual to be that Gong amount by material decides, but under regular service conditions, described nuclear will can not carry and surpass above-mentioned percentage elongation.In addition, described nuclear has low compressibility.Compressibility can be counted as being inversely proportional to bulk modulus (bulk modulus).Usually the bulk modulus of 1GPa will be high fully.In fact this can be provided by all rubber and colloidal material, supposes that they seldom contain the words of air or other gas.Under the situation that adopts this kind nuclear, the variation of localised load for example when rachiocamposis, can be converted into the change of shape of whole nuclear.Therefore, will cause not existing outstanding on another aspect of load the pressing down that material is carried out of the localised load on the point.The behavior is to a great extent corresponding to the function of natural nucleus in the intervertebral disc.

Described nuclear has the shape of flat partially body, has upper side and downside." partially flat " is understood that at this: the vertical dimension between upper side and the downside, than with the vertical direction of this distance on size much smaller, for example at least will be divided by the factor 2.In fact, described upper side and downside also need not be fully smooth, and can be for example to have the core thicker or thinner than marginal area, for example make nuclear have the shape of lens.The upper side of nuclear and downside are preferably justified shape; This means that above-mentioned lateral edge does not have the part at ledge or one-tenth angle on its plane, for example, because edge's minimum profile curvature radius is at least 10mm.Obtained following effect thus: when described dish be in the load following time, the pressure of generation is evenly distributed on the whole twister, this has reduced local outstanding risk to a great extent.More preferably, described upper side and downside are circular or oval-shaped, like this can be in side surface---be also referred to as " side surface " hereinafter and go up and obtain pressure distribution the most uniformly.In addition, described endorsing so that the hole to be arranged in the central makes it have annular or corresponding shape.

The suitable material that is used to examine is biocompatible materials preferably, for example has been widely used in silicone rubber, polyurethane rubber, acrylate rubber, EP (D) M rubber and other rubber-like or the colloidal material of the type that body is implanted into.Yet the biocompatibility of rubber is not strict condition, supposes the words in the packaged biocompatible membrane that advances to seal of described rubber.But aspect flexible and low hydrostatic compression property, described material should always can satisfy the condition that above proposes.Therefore described nuclear can or even be packaged in the form of the liquid in the biocompatible capsule, and described capsule self should be enough soft, to bear the change of shape that load causes.

Around nuclear, along at least roughly radially apply the traction-resistant fibre twister.Can be allowed around the twister that applies of nuclear to examine in the certain change of shape of spinal column on vertically like this, but on perpendicular to the direction of spinal column, not allow or only seldom allow.The change of shape of the nuclear that like this, just having avoided loads causes causes nuclear to be projected into outside the vertebral body.It is big when the shape of spinal column on vertically becomes change scope (flexibility) and seem when underload than high load capacity.Therefore seem just had the longitudinal elasticity characteristic of improving according to the nuclear in the dish of the present invention.Because the high initial flexibility has vertically been guaranteed good shock absorbing, and the flexibility that reduces under higher load has guaranteed that the distance between the vertebra prevents enough that still nerve is blocked, so this is a main advantage.

Twister substantially radially extends.This is understood that twister extends across downside and upper side, at least 50% in the twister according to following path across downside and upper side: described path to about the minimum range of side center of gravity equal downside and upper side maximum sized 30% at the most.In addition, twister in the road from the downside to the upper side across side surface.Fiber preferably with an angle across side surface, described angle and perpendicular to up and down between the side the direction of short line depart from maximum 55 °.Be good across having different angles between the fiber of side surface and described vertical direction.Have low-angle fiber nuclear is had strong stablizing effect.For bearing the torque load that may betide between the two joint vertebras, the fiber with 45 is best.Therefore fiber extends along geodesic curve (geodetic line) basically, and described side ground wire is the shortest connecting line of examining between surperficial 2.Fibre direction variations on upper side and downside mentioned above provides such benefit: it has prevented the accumulation of fibers and the consequent partial thickening at center of gravity place.Variation on the described side surface provides such benefit: the twisting resistance that puts on the dish has been born effectively.Therefore, also avoided causing fiber towards shorter path displacement easily across nuclear owing to the tension force that puts on the fiber that the load on the nuclear produces.Such displacement may cause that people do not expect to producing weakening of outstanding opposing.

With regard to regard to the extra inhibition that may be shifted of twister under load, if successive twister not exclusively is placed on the top of each other, but the alternatively up and down of the twister that the fiber of twister formerly has been placed connects several times, can be good.The dipping glue-like substance also helps to prevent described displacement.For such dipping, use the biocompatible tissue sicker to be good, because it promotes bonding between described dish and the vertebral body.

Except the twister that substantially radially extends, the preferred twister that also has fully the traction-resistant fibre of extending across side surface.This provides the extra obstruction that nuclear is projected into the outer generation of dish.

Since between nuclear and the twister of traction-resistant fibre along side surface at least and at least the part of the lateral part of infra and upper side have fabric, can obtain through further improved dish giving prominence to the opposing of generation.Described fabric is preferably close to be knitted, thereby combines with fiber around its winding, makes that the material of any nuclear all can not overflow from described fabric under load.If under given combination, because issuable load in practice, the material of nuclear may overflow, and then those skilled in the art also can be easy to this is improved by selecting closeer fabric and/or closeer canoe.Within other local institute restricted portion, the material of selecting to have higher modulus of shearing also is fine in this article.

From US 5,824, a kind of prosthese that is used for replacing at the nuclear of natural disc of cicada in 093, described prosthese is made up of the hydrogel core that woven bag surrounds.After intervertebral disc removed, two prostheses were placed in the space that forms thus with natural nuclear.Described prosthese does not fill up whole space, and this has limited outstanding risk.In addition, natural endless belt (annulus) still exists, and it was wrapped in natural nuclear in the past, then was wrapped in prosthese now.Described document does not provide any hint about the prosthese that makes up whole intervertebral disc, does not relate to the structure according to intervertebral disc of the present invention.In addition, only will be wrapped in the textile bags according to the nuclear in the dish of the present invention, be to be enough to anything but prevent to examine under load give prominence to.This mainly is to be used for displacement because fiber can obtain a lot of spaces, and because the high construction stretch in the fabric.In addition, the fibre length in this kind fabric is very short, has reached the magnitude of described bag.The load that produces on fiber requires bigger length usually.The intensity of the fiber in this kind bag thereby also just do not used fully.In dish according to the present invention, be preferably formed the part of individual filaments across the twister of downside and upper side extension.If used some silks, its length preferably equals at least 10 times of the girth examined, and described girth is to measure along the side ground wire of walking around center of gravity.Optionally the twister across side surface also preferably is made of single filament.If used some silks for this reason, the length of each bar all preferably equals at least 10 times of girth of the nuclear measured across its side surface so.

In this article, be at the most 15% as the elongation at break of fruit fiber, preferably at the most 5%, this fiber just is considered to tension so.Described fiber preferably has at least 10GPa, the preferred modulus of shearing of 75GPa at least, and has 1GPa at least, is preferably the tensile strength of 2GPa at least even 2.5GPa.

The material of described fiber should be that health is receptible, does not cause any inflammation, decomposition or other bad reaction therein, nor dissolves therein, decomposes or the degraded of other modes.Therefore suitable material for example is polyethylene (particularly high molecular weight type), aramid fiber, carbon, polybenzoxazole, poly-(2,6-diimidazole also [4,5-b 4 ', 5 '-e] pyridine support-1,4-(2, the 5-dihydroxy)-and penylene) (poly (2,6-diimidazo[4,5-b4 ', 5 '-e] pyridinylene-1,4 (2,5-dihydroxy) phenylene)) and polyethylene terephthalate.Other fiber that reaches the material of described requirement also is applicable to according to dish of the present invention.

The rugosity of forming the fiber of twister can change in very wide limited field, for example at 50dtex between the 2000dtex, it can be that monofilament also can be a multifilament.Usually,, then compare, can obtain better parcel for nuclear with more coarse-fibred form of still less twining pari passu if the fibrous material of specified rate appears in the twister with the form than more windings of fine fibre.Suppose twister form unanimity, the described structure in the previous case is than a kind of closeer in back.

In addition, the material or the chemical compound that promote skeletal tissue to increase can be applied to or be coated on the described fibrous material, and described skeletal tissue grows on the twister or between it from the vertebral body that contacts with described dish, perhaps grow on the fabric of any existence or between it.This is with promotion dish fixing with respect to adjacent vertebral bodies.For the purpose of the initial fixation of the vertebral body of dish of the present invention having been placed relatively dish of the present invention therebetween, can give described dish setting outstanding towards the vertebral body orientation.

By coming to apply fiber, can produce according to artificial intervertebral disc of the present invention around nuclear with desired form as described in the text.This can finish by manual, also can finish under the help of the machine of being equipped for this purpose.Can flood nuclear, perhaps make it comprise the chemical compound of the effect of people's physical ability performance people being wanted as chemical compound such as growth promoter, inflammation inhibitor, antibiotic and other its processing of carrying out other modes.

The technical staff will be very clear: though a kind of artificial intervertebral disc has only been described in the preamble,, have similar structures and variform dish or object also go for other application; Include but not limited to other medical application, for example prosthese.The shape and size of this type of dish or other object can purposes concrete with it adapt; For example, synthetical knee meniscus.

Accompanying drawing now with reference to the back comes the present invention is set forth, and wherein, Fig. 1 is according to the manual dish that twines according to the present invention, and Fig. 2 is power that the dish among Fig. 1 the is measured curve to displacement.

In Fig. 1, not visible nuclear exists with the form of cylindrical disc, the diameter of described dish is 38.5mm, thickness is 15mm, it is that about 5MPa, elongation at break are that silicone rubber about 200%, that bulk modulus is about 1.5GPa is made by modulus of shearing, described nuclear is wrapped up by the fabric 2 of tension polyethylene fibre, and described fabric some point between twister 4 and 6 remains visual.Exist across downside and the twister 4 of upper side and side surface extension and the twister 6 that only extends around it across side surface.Described fiber is made of two strands of twisting multifibres, and per share is 440dtex, is made by High molecular weight polyethylene.The described fiber that has been used to fabric and twister is made of gel-spun high-molecular PE, and its tensile strength is 3.6GPa, and modulus is 115GPa.Elongation at break is 3.5%.

Drawn out the figure that suffered power F is done this caused deflection L that loads in Zwick 1484 universal testing machines of the dish among Fig. 1 in Fig. 2, described power F represents that with kN deflection L represents with mm.Can be clear that, after displacement reaches the clamped start-up period of its mid-game of 1mm, at load curve the phase I from 1mm to about 2-2.5mm, only need very little power just can obtain certain displacement, and stage in the end, from 2.5mm, needed power has increased a lot.This curve chart means that described dish has the flexibility of height concerning less power, and simultaneously, it is very high that it absorbs the ability that puts on the stronger power on the dish with very little relatively distortion.Look that it is just destroyed up to described dish having been applied above after the power of 7kN, this is equivalent to the load of about 700kg, is higher than the power that human spine's reality is born far away.

Claims (9)

1. artificial intervertebral disc comprises the nuclear of flexible material, and described nuclear has the shape of flat partially body, has the downside and the upper side that connect by side surface, has applied at least substantially radially directed traction-resistant fibre twister around described nuclear.

2. intervertebral disc as claimed in claim 1, wherein said downside and described upper side are the circle shapes, and be preferably circular or oval.

3. intervertebral disc as claimed in claim 1 or 2, wherein, described twister extends across the surface of nuclear along geodesic curve basically.

4. as any described intervertebral disc among the claim 1-3, wherein, described fiber has the tensile strength of 1GPa at least and the modulus of 10GPa at least.

5. as any described intervertebral disc among the claim 1-4, wherein, described fiber is made of polyethylene.

6. as any described intervertebral disc among the claim 1-5, wherein, also there is the traction-resistant fibre twister that extends across described side surface fully.

7. as any described intervertebral disc among the claim 1-6, wherein, between described nuclear and described fiber, have fabric along the part of described at least side surface and described at least downside and the part of upper side.

8. intervertebral disc as claimed in claim 7, wherein, described fabric is made of traction-resistant fibre.

9. intervertebral disc as claimed in claim 8, wherein, described fiber has the tensile strength of 1GPa at least and the modulus of 10GPa at least.